So backstory, my boyfriend has this online "friend" that he's known for just under a decade. He hasn't been in a serious relationship since he started talking to her until we got together. We got together 2 years ago. When I found out about her and saw some of their messages I was immediately uncomfortable. The way they talked was more like bf/gf. How much they cared about each other, and even some more explicit things, like talking about the kind of underwear she wears. I was obviously upset and we had some arguments, and I told him he needed to set boundaries. Turns out, they never did, and they actually mocked me for being uncomfortable with the intimacy in their friendship. They got very close during my pregnancy (baby is 3 months old now) before that they talked maybe once a week, during my pregnancy it escalated to almost all day every day. Keep in mind, we're in super different time zones, we're in the US and she is somewhere in the UK. He literally changed his sleep habits to be up and talk to her during her mornings, while I went to bed alone. About a month ago I found out about them mocking me and continuing their relationship. I told him at that point that I am not going to be anyone's second choice, he doesn't get 2 girlfriends, and he needs to choose who he wants to continue a relationship with. Me or her. He was very upset and she called me manipulative, and tried to get him to leave me. He did choose me, but afterwards, he sulked like he had gone through a breakup. That only proved to me that their relationship was definitely more than just friends. But one of his male friends also said I was manipulative, and my boyfriend does seem really hurt. Am I the buttface? UPDATE: I found out this morning he lied about how long he's known her. It's only been about 3/4 years. He really did try to tell me that he was closer friends with her because he's known her longer and been friends with her longer than anybody else currently in his life. He met his best IRL friend in 2012.